1. Field of the Invention
This invention relates to an apparatus having a vacuum chamber, in which a sputtering process is performed, e.g., for use in a continuous sputtering system. More particularly, this invention relates to the improvement of a piping apparatus having valve mechanism suitable for a load-lock chamber in which an object to be processed is transferred in and out between atmospheres different in pressure.
2. Description of the Prior Art
A compact disk (hereinafter, referred to as a CD) has been widely used to record a large amount of digitized sound and image information. The substrate of the CD is made of transparent synthetic resin on the surface of which a large number of so-called pits are formed in accordance with digital information of "1" or "0". An aluminum thin film layer having high light reflectivity is deposited on the thus formed surface by use of a sputtering technique. The thus recorded information is read by the presence or absence of the reflected light or penetrated light of a laser light beam applied to the CD.
The aluminum thin film deposition of a single substrate can be performed in a relatively short period. Thus, a continuous sputtering system shown in FIG. 5 has been used.
In FIG. 5, a transferring chamber 3 having a sputtering chamber 41 and a load-lock chamber 31 is connected to an exhaust pump 6A so as to be exhausted. The transferring chamber 3 serves to transfer a substrate 1, which is an object to be sputtered, from load-lock chamber 31 to sputtering chamber 41, and also to hold sputtering chamber 41 in the exhausted atmosphere. A receptor 32, which performs reciprocating motion between load-lock chamber 31 and sputtering chamber 41, is provided in transferring chamber 3. The load-lock chamber 31 is situated at a position in the vicinity of sputtering chamber 41, i.e., in a part of an upper lid 30 of transferring chamber 3. Specifically, load-lock chamber 31 is constituted by the inner walls of an opening 34 made in the upper lid 30, the receptor 32 and a load-lock lid 22. The receptor 32 hermetically touches the lower side of the opening 34. The load-lock lid 22, which transfers substrate 1 by sucking, serves to hermetically plug the opening 34.
When opening 34 is hermetically closed by receptor 32 from the inside, transferring chamber 3 becomes hermetically sealed. Thereafter, transferring chamber 3 is exhausted by use of exhaust pump 6A. Thus, sputtering chamber 41 is exhausted to the degree of vacuum such that a prescribed sputtering process can be performed.
On the other hand, opening 34 is plugged by load-lock lid 22, which has transferred substrate 1 using sucking pads operated by an exhaust system 6D. This constitutes load-lock chamber 31. However, the pressure in load-lock chamber 31 is still at the atmospheric pressure. If receptor 32 is moved in order to transfer the received substrate 1, the hermetic sealing state of opening 34 is inevitably released. Thus, the atmosphere in load-lock chamber 31 flows into transferring chamber 3, and decreases the degree of vacuum in transferring chamber 3 and sputtering chamber 41. As a result, valuable time must be wasted to recover the prescribed degree of vacuum for sputtering by use of the exhaust pump 6A. Therefore, an exhaust system 6B is connected to an opening made in the wall of load-lock chamber 31 so that load-lock chamber 31 can be previously exhausted. Further, when load-lock chamber 31 is exhausted by the exhaust system 6B, the pressure in load-lock chamber 31 becomes a negative pressure. This is because substrate 1 has been sucked by sucking pads to load-lock lid 22. When the vacuum source of the sucking pads is isolated, substrate 1 is released from the suction pads, and transferred to receptor 32. Thereafter, receptor 32 transfers the thus received substrate 1 to sputtering chamber 41 and presses substrate 1 against a masking portion 43 of the sputtering chamber 41. While remaining in this state, the sputtering process is performed so as to deposit an aluminum thin film on the surface of substrate 1. After the completion of the sputtering process, receptor 32 transfers substrate 1 to the load-lock portion, and hermetically touches opening 34 so as to constitute load-lock chamber 31. Thereafter, an intake system 6C, which is connected to an opening made in the wall of load-lock chamber 31, introduces the atmospheric pressure into load-lock chamber 31. Subsequently, the sucking pads are exhausted to a vacuum, and substrate 1 is sucked by the sucking pads to load-lock lid 22. The pressure in load-lock chamber 31 has been at the atmospheric pressure. Thus, load-lock lid 22 can be easily removed from the opening 34, and moved upward in a direction indicated by arrow 23 shown in FIG. 5. As a result, substrate 1 can be transferred to a subsequent process.
As described above, transferring chamber 3 can be maintained in the prescribed exhaust state throughout the processes such as the reception and delivery of substrate 1, and the sputtering. Further, substrate 1 can be smoothly transferred between the load-lock lid 22 and susceptor 32 by virtue of the approriate exhaust and intake with respect to load-lock chamber 31. Thus, the continuous sputtering system can be operated in which a large number of disk substrates can be sputtered in a short time.
The conventional exhaust and intake mechanisms of load-lock chamber 31 will be described with reference to FIGS. 6 and 7. Specifically, a common passage 61 is formed extending from an opening made in the wall of load-lock chamber 31 to an outside end. A bifurcated pipe 62, an exhaust valve 71, an intake valve 72, pipes 81 and 82, and an exhaust pump (not shown) are connected through a flange F to the outside end of common passage 61.
More specifically, when substrate 1 is transferred from load-lock lid 22 to receptor 32, substrate 1 is transferred into transferring chamber 3, and then load-lock chamber 31 must be exhausted. As shown in the enlarged view of FIG. 6, common passage 61, which serves both as an exhaust bore and as an intake bore, is connected to the external rotary pump (not shown) through bifurcated pipe 62 and exhaust valve 71. When exhaust valve 71 is opened, load-lock chamber 31 is coarsely exhausted to an intermediate degree of vacuum, and substrate 1 is transferred from load-lock lid 22 to receptor 32. Thereafter, receptor 32 is moved downward, and exhaust pump 6A is operated so as to exhaust transferring chamber 3 and load-lock chamber 31 to a higher degree of vacuum.
When the sputtered substrate 1 is transferred from receptor 32 to load-lock lid 22, the pressure in load-lock chamber 31 is changed to the atmospheric pressure in the following manner. Specifically, valve 71 is closed, and valve 72, which is connected to the other end of bifurcated pipe 62 as shown in FIG. 7, is temporarily opened so as to introduce the atmospheric pressure into load-lock chamber 31. As a result, the sputtered substrate 1 can be sucked by the sucking pads, which are exhausted by exhaust system 6B, to load-lock lid 22, and transferred to the outside. In FIG. 6, reference characters L represent O-rings for sealing, and reference numerals 81 and 82 in FIG. 7 represent pipes connected to the rotary pump and the atmospheric space, respectively.
However, as described above, the conventional piping apparatus must have the bulky valve mechanism and lengthy pipes in order to achieve the connection from load-lock chamber 31 to the exhaust rotary pump and to the atmospheric space. This is because valves 71 and 72, which are operated independently, must be connected to bifurcate pipe 62 and the like using bolts. Therefore, the conventional piping apparatus has the following disadvantages. Specifically, the bulky valve mechanism inevitably causes the apparatus to be large-sized, and the lengthy intake-exhaust piping decreases the conductance (the reciprocal of resistance of gas-flow). As a result, the function of load-lock chamber 31 as a boundary chamber between the atmosphere and vacuum cannot be sufficiently obtained.
Such disadvantages also exist in the case when valve 72 is omitted, and valve 71 is directly connected to common passage 61 in order to serve as an exclusive use for exhaust.
As described above, in the conventional piping apparatus having valve mechanism, a common passage is formed in the wall of a vacuum chamber (e.g., a load-lock chamber to be exhausted to a vacuum). However, such a common passage must be connected to independent valves provided outside the chamber. Thus, the piping apparatus inevitably becomes large-sized, and the conductance with respect to the gas-flow decreases.